1. Field of the Invention
This invention relates to a photographic lens, and more particularly to a lens shutter photographic lens having a half-angle of view of about 32.degree. and F4.0 as well as being compact.
2. Description of the Prior Art
With the trend of compactness of a camera using a lens shutter, a demand of formation of a photographic lens into compactness is also increased. To this end, various proposals have been made for lenses of the inverted retrofocus type in which a negative meniscus lens having a great curvature toward an image is arranged at the rear of a triplet of convex, concave and convex.
In well known photographic lenses of the type as described above, the lens disclosed, for example, in Japanese Patent Laid-Open Application No. 73014/80 has four lenses which are all formed of glass material and which has a refractive index larger than 1.6. In Japanese Patent Publication Nos. 75612/81 and 94317/81, a negative second lens has a refractive index above 1.7. As described above, in these lenses, particularly the second lens has a high refractive index, N&gt;1.65, and it has been difficult to form this lens into a resin lens. Further, in Japanese Patent Laid-Open No. 99313/81, it is found that a refractive index of material for the second, third and fourth lenses is N&lt;1.65, and a telephoto ratio is about 1.10, which is insufficient in terms of compactness of the entire lens system.